1. Field of the Invention
With reference to the classification of art as established in the U.S. Patent and Trademark Office the present invention is believed to be found in the general Class entitled, "Turning" (Class 82) and more particularly in the subclass entitled, "Lathe-Centers" (subclass 33R).
2. Description of the Prior Art
Live centers are well known and in particular the use of hydraulic gages to indicate the thrust or load on the rotating center members is known and is shown in the prior art. In particular, reference is made to U.S. Pat. No. 2,844,063 as issued to ROHM on July 22, 1958. In this patent is shown a hydraulic gage which is carried by the housing and which is actuated by the longitudinal motion of the rotating spindle as it is moved rearwardly by the developed thrust of and by the workpiece. In the live center of the ROHM patent and in others known to the Applicant there has been no attempt to accept a full thrust on a heavy-duty live center disposed to carry a heavy workpiece. After a workpiece has been mounted in a live center and the work member is subject to the process of finishing it often becomes heated to cause a further thrust load upon the live center.
In particular, the live center and hydraulic reading as seen in ROHM anticipates and requires that the rotatable center member which is supported by the bearing is movable directly against a hydraulic reservoir. In heavy-duty live centers such a movement and the bowing of the center spindle as detailed in my above-identified application is not acceptable and/or cannot be tolerated. Accuracy of the live center during all periods of use requires that the revolving center member be fully retained against any longitudinal movement that might result in deviations. In the invention, as depicted, both the rotating center and the quill or housing are carried in the tailstock of the lathe or grinder. The live center as a unit is moved by a screw in the tailstock of the lathe or grinder. This screw actuates or moves a nut which carries a series of Belleville-type washers or springs which have the capacity to accept the anticipated longitudinal thrust or expansion of the workpiece as carried by the live center. A totally or completely closed, hydraulic, circular cell and reservoir are carried in and by this quill or housing and have a protruding portion of the cell resting against and pushed by the Belleville-type springs. These Belleville-type springs accept the increased thrust as is produced by heating of the workpiece. This expansion is accommodated without disturbing and destroying the alignment of the revolving center as carried in the quill and by the thrust and radial bearings. A bowing of the revolving center member which occurs under heavy loads does not affect the hydraulic load cell which is carried in the rear portion of the quill or housing. The bowing of the rotating center portion of the heavy-duty live center is accommodated in the present heavy-duty live center.